During the 1970s there was a gross loss of public confidence in infant diphtheria-tetanus-pertussis (DTP) vaccination in the UK. As well as febrile reactions and convulsions, permanent neurological damage was ascribed to the pertussis component of the vaccine, and those concerns resonated worldwide. The subsequent recognition of human herpes virus 6 (HHV-6) and 7 (HHV-7) as common sources of fever in infancy suggests that they were the main underlying cause of what was reported as DTP constitutional side-effects. With more precise data on the incidence of HHV-6/7 and other virus infections in early life it would be possible to model the concurrence of viral illnesses with routine immunizations. Adventitious viral infections may be the cause of side-effects ascribed to the numerous childhood immunizations now being given.
